Hydrogels have been recently attracting attention from the viewpoint that hydrogels are soft materials having high biocompatibility because of containing water as the main component and having a low environmental load.
As a high-strength hydrogel having a self-supporting property, an organic/inorganic composite hydrogel is disclosed that is obtained by performing a polymerization reaction of a (meth)acrylamide derivative in the coexistence with a layered clay mineral that is uniformly dispersed in water (Patent Document 1). As a similar example disclosed, an organic/inorganic composite hydrogel is also known that contains a polymer partially containing a group of a carboxylate salt or a carboxy-anion structure in poly(meth)acrylamide and a clay mineral (Patent Document 2).
In these examples disclosed, monomers are polymerized in an aqueous dispersion of a layered clay mineral, thereby causing a generated polymer and the clay mineral to form a three-dimensional network structure, which forms the organic/inorganic composite hydrogels.
An organic/inorganic composite polymer gel is known that contains an organic polymer obtained from a water-soluble organic monomer selected from acrylamides and methacrylamides, a water-swellable clay mineral, and a low-volatile medium such as glycerin and is produced through a hydrogel containing glycerin or the like (Patent Document 3).
As an organic/inorganic composite hydrogel having a self-supporting property that can be manufactured through mixing at room temperature, a hydrogel is known that is obtained by mixing a dendrimer compound having a polycationic functional group at its terminal and a layered clay mineral (Patent Document 4 and Non-Patent Document 1).
A dry clay film having a self-standing property (self-supporting property) is known that contains a polyacrylate salt and a clay mineral and is under evaluation as a surface protective material (Patent Document 5).
A research is known that relates to viscosity changes in an aqueous dispersion of a layered clay mineral (silicate salt) and sodium polyacrylate (Non-Patent Document 2). This is not a research related to a self-supporting organic/inorganic composite hydrogel, but a research on rheological changes in the aqueous dispersion.
Organic/inorganic composite hydrogels having a self-supporting property have been recently disclosed that can be produced only by mixing a polyelectrolyte, clay particles, and a dispersant (Non-Patent Document 3 and Non-Patent Document 4).